Electronic devices, such as radios and other receiving electronic systems, are configured to receive signals via radio waves. The radio waves are propagated via different frequencies. Each frequency may correspond to a specific channel or source of information. In a vehicle, the electronic device may be provided with a radio frequency (RF) receiver, and in response to a specific RF being tuned to, the RF receiver may be configured to receive the signal associated with radio waves of the specific RF frequency.
Various digital signal processing (DSP) techniques may be employed by the RF receiver to improve and augment the signal being received. One such element is a radio frequency auto gain control (RF AGC) circuit or device. The RF AGC prevents the received antenna signals from overloading a front-end circuit. An overloading of a front-end circuit is caused by a signal over a specific amount being received at an input end of the RF receiver. The signal may be received from either the intended signal to be received (the frequency being tuned into) or a non-intended signal being received (another frequency).
Conventional RF AGC's address this issue by reducing a gain and/or sensitivity over the whole band. A band is all the available frequencies capable of being tuned into via a RF receiver. By doing this, the overall sensitivity (i.e. the ability to pick up signals) by a RF receiver is reduced. This phenomenon is labeled as desensitization.
This desensitization may cause problems with overall reception. For example, if the RF receiver is tuned into a specific frequency that is relatively weak, the desensitization may cause the signal's strength to reduce to a level that is not acceptable.
FIG. 1 illustrates an example graph 100 explaining phenomena explained above. The x-axis 110 shows an input RF signal strength, and the y-axis 120 shows audio output signal strength. Several signals are shown, such as a signal without RF AGC 130, and a signal with 18 decibels of RF AGC 140. Further, the noise is plotted for both, so the noise is plotted with the signal without RF AGC 150 and the noise for the signal with 18 dB RF AGC 160.
As shown in point 170, the signal-to-noise (SNR) ratio is 48 dB for the case of a signal with RF AGC and 67 dB in the case without RF AGC. This graph 100 illustrates that as the signal gets weaker, the noise floor (i.e. noise signal 160) goes higher. Thus, with a larger SNR, the signal 120 is less likely to provide an effective quality rate required to provide certain services (such as high definition radio).
FIG. 2 illustrates an example of a single and dual-tuner receiver 200 according to a conventional implementation. The receiver 200 includes an input stage 210, a digital signal processor (DSP) 220, an audio power amplifier 230, a microcontroller 240, and a speaker 250. Due to this receiver 200 being known in the art, a detailed explanation will be omitted. Essentially, a DSP may implement an improvement of signal strength and quality by including various chipsets dedicated to providing AGC.